Rechargeable batteries, particularly nickel-metal hydride (NiMH) batteries, are useful in many types of applications. For example, the batteries may be used as a backup power supply for stationary applications such as cellular towers. The batteries provide backup power during a main grid outage. In such an application, it is desirable that the batteries are connected to a battery charging circuit that maintains the state of charge of the batteries. Under certain circumstances, charging NiMH batteries may cause the batteries to overheat, which may damage the batteries or other components.